Levulinic acid has been identified as a suitable chemical feedstock that can be processed from hexose sugars derived from biomass. Its conversion into γ-valerolactone (gammavalerolactone, GVL) via hydrogenation and ring closure to the lactone is a promising route to the manufacture of renewable components, for various syntheses, to be used as fuel components or for suitable uses as such.
Conversion of levulinic acid to γ-valerolactone has been reported in U.S. Pat. No. 6,617,464B2. Different catalysts able to perform the hydrogenation and ring closure needed for this reaction were studied and compared. The conversions were performed at a high temperature, 215° C.
Another document disclosing a process for conversion of levulinic acid to γ-valerolactone and further to products such as adipic acid and ammonium adipate is EP2537840B1. The conversion was performed at 130° C. in the presence of at least 0.08% water relative to the amount of levulinic acid. Even though results show high selectivity, was the levulinic acid conversion not satisfactory varying between 51-79%.
Chalid et al. (M. Chalid et al., Green polymer precursors from biomass-based levulinic acid, Procedia Chemistry 4 (2012), pages 260-267) have reported a pathway from levulinic acid to various γ-hydroxy-amides for use as polymer precursors. One step in the process therein reported was the biphasic hydrogenation of levulinic acid to γ-valerolactone using homogenous water-soluble Ru-(TPPTS) catalyst. The reaction proceeded through 4-hydroxypentanoic acid (4-hydroxyvaleric acid, 4-HVA) intermediate product, which was not very stable and reacted easily to gammavalerolactone through cyclization reactions. Even though levulinic acid was quickly converted (98%) at 90° C., the ring closure to gammavalerolactone was not complete after 60 min reaction time.
Hence, there still is need to control the reaction pathway and further optimize the yield of gammavalerolactone as end product. A process is disclosed herein for conversion of levulinic acid with better selectivity towards γ-valerolactone. The γ-valerolactone recovery can be improved in the process. The conversion of levulinic acid can be run under process conditions, wherein hydrogenation side products are minimized.